{ config, lib, pkgs, ... }:

with lib;

{

  options = {

    systemd.package = mkOption {
      default = pkgs.systemd;
      defaultText = literalExpression "pkgs.systemd";
      type = types.package;
      description = "The systemd package.";
    };

    systemd.units = mkOption {
      description = "Definition of systemd units.";
      default = {};
      type = with types; attrsOf (submodule (
        { name, config, ... }:
        { options = concreteUnitOptions;
          config = {
            unit = mkDefault (makeUnit name config);
          };
        }));
    };

    systemd.packages = mkOption {
      default = [];
      type = types.listOf types.package;
      example = literalExpression "[ pkgs.systemd-cryptsetup-generator ]";
      description = "Packages providing systemd units and hooks.";
    };

    systemd.targets = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = targetOptions; } unitConfig] );
      description = "Definition of systemd target units.";
    };

    systemd.services = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = serviceOptions; } unitConfig serviceConfig ]);
      description = "Definition of systemd service units.";
    };

    systemd.sockets = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = socketOptions; } unitConfig ]);
      description = "Definition of systemd socket units.";
    };

    systemd.timers = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = timerOptions; } unitConfig ]);
      description = "Definition of systemd timer units.";
    };

    systemd.paths = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = pathOptions; } unitConfig ]);
      description = "Definition of systemd path units.";
    };

    systemd.mounts = mkOption {
      default = [];
      type = with types; listOf (submodule [ { options = mountOptions; } unitConfig mountConfig ]);
      description = ''
        Definition of systemd mount units.
        This is a list instead of an attrSet, because systemd mandates the names to be derived from
        the 'where' attribute.
      '';
    };

    systemd.automounts = mkOption {
      default = [];
      type = with types; listOf (submodule [ { options = automountOptions; } unitConfig automountConfig ]);
      description = ''
        Definition of systemd automount units.
        This is a list instead of an attrSet, because systemd mandates the names to be derived from
        the 'where' attribute.
      '';
    };

    systemd.slices = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = sliceOptions; } unitConfig] );
      description = "Definition of slice configurations.";
    };

    systemd.generators = mkOption {
      type = types.attrsOf types.path;
      default = {};
      example = { systemd-gpt-auto-generator = "/dev/null"; };
      description = ''
        Definition of systemd generators.
        For each <literal>NAME = VALUE</literal> pair of the attrSet, a link is generated from
        <literal>/etc/systemd/system-generators/NAME</literal> to <literal>VALUE</literal>.
      '';
    };

    systemd.shutdown = mkOption {
      type = types.attrsOf types.path;
      default = {};
      description = ''
        Definition of systemd shutdown executables.
        For each <literal>NAME = VALUE</literal> pair of the attrSet, a link is generated from
        <literal>/etc/systemd/system-shutdown/NAME</literal> to <literal>VALUE</literal>.
      '';
    };

    systemd.defaultUnit = mkOption {
      default = "multi-user.target";
      type = types.str;
      description = "Default unit started when the system boots.";
    };

    systemd.ctrlAltDelUnit = mkOption {
      default = "reboot.target";
      type = types.str;
      example = "poweroff.target";
      description = ''
        Target that should be started when Ctrl-Alt-Delete is pressed.
      '';
    };

    systemd.globalEnvironment = mkOption {
      type = with types; attrsOf (nullOr (oneOf [ str path package ]));
      default = {};
      example = { TZ = "CET"; };
      description = ''
        Environment variables passed to <emphasis>all</emphasis> systemd units.
      '';
    };

    systemd.enableCgroupAccounting = mkOption {
      default = true;
      type = types.bool;
      description = ''
        Whether to enable cgroup accounting.
      '';
    };

    systemd.enableUnifiedCgroupHierarchy = mkOption {
      default = true;
      type = types.bool;
      description = ''
        Whether to enable the unified cgroup hierarchy (cgroupsv2).
      '';
    };

    systemd.coredump.enable = mkOption {
      default = true;
      type = types.bool;
      description = ''
        Whether core dumps should be processed by
        <command>systemd-coredump</command>. If disabled, core dumps
        appear in the current directory of the crashing process.
      '';
    };

    systemd.coredump.extraConfig = mkOption {
      default = "";
      type = types.lines;
      example = "Storage=journal";
      description = ''
        Extra config options for systemd-coredump. See coredump.conf(5) man page
        for available options.
      '';
    };

    systemd.extraConfig = mkOption {
      default = "";
      type = types.lines;
      example = "DefaultLimitCORE=infinity";
      description = ''
        Extra config options for systemd. See man systemd-system.conf for
        available options.
      '';
    };

    services.journald.console = mkOption {
      default = "";
      type = types.str;
      description = "If non-empty, write log messages to the specified TTY device.";
    };

    services.journald.rateLimitInterval = mkOption {
      default = "30s";
      type = types.str;
      description = ''
        Configures the rate limiting interval that is applied to all
        messages generated on the system. This rate limiting is applied
        per-service, so that two services which log do not interfere with
        each other's limit. The value may be specified in the following
        units: s, min, h, ms, us. To turn off any kind of rate limiting,
        set either value to 0.

        See <option>services.journald.rateLimitBurst</option> for important
        considerations when setting this value.
      '';
    };

    services.journald.rateLimitBurst = mkOption {
      default = 10000;
      type = types.int;
      description = ''
        Configures the rate limiting burst limit (number of messages per
        interval) that is applied to all messages generated on the system.
        This rate limiting is applied per-service, so that two services
        which log do not interfere with each other's limit.

        Note that the effective rate limit is multiplied by a factor derived
        from the available free disk space for the journal as described on
        <link xlink:href="https://www.freedesktop.org/software/systemd/man/journald.conf.html">
        journald.conf(5)</link>.

        Note that the total amount of logs stored is limited by journald settings
        such as <literal>SystemMaxUse</literal>, which defaults to a 4 GB cap.

        It is thus recommended to compute what period of time that you will be
        able to store logs for when an application logs at full burst rate.
        With default settings for log lines that are 100 Bytes long, this can
        amount to just a few hours.
      '';
    };

    services.journald.extraConfig = mkOption {
      default = "";
      type = types.lines;
      example = "Storage=volatile";
      description = ''
        Extra config options for systemd-journald. See man journald.conf
        for available options.
      '';
    };

    services.journald.enableHttpGateway = mkOption {
      default = false;
      type = types.bool;
      description = ''
        Whether to enable the HTTP gateway to the journal.
      '';
    };

    services.journald.forwardToSyslog = mkOption {
      default = config.services.rsyslogd.enable || config.services.syslog-ng.enable;
      defaultText = literalExpression "services.rsyslogd.enable || services.syslog-ng.enable";
      type = types.bool;
      description = ''
        Whether to forward log messages to syslog.
      '';
    };

    services.logind.extraConfig = mkOption {
      default = "";
      type = types.lines;
      example = "IdleAction=lock";
      description = ''
        Extra config options for systemd-logind. See
        <link xlink:href="https://www.freedesktop.org/software/systemd/man/logind.conf.html">
        logind.conf(5)</link> for available options.
      '';
    };

    services.logind.killUserProcesses = mkOption {
      default = false;
      type = types.bool;
      description = ''
        Specifies whether the processes of a user should be killed
        when the user logs out.  If true, the scope unit corresponding
        to the session and all processes inside that scope will be
        terminated.  If false, the scope is "abandoned" (see
        <link xlink:href="https://www.freedesktop.org/software/systemd/man/systemd.scope.html#">
        systemd.scope(5)</link>), and processes are not killed.
        </para>

        <para>
        See <link xlink:href="https://www.freedesktop.org/software/systemd/man/logind.conf.html#KillUserProcesses=">logind.conf(5)</link>
        for more details.
      '';
    };

    services.logind.lidSwitch = mkOption {
      default = "suspend";
      example = "ignore";
      type = logindHandlerType;

      description = ''
        Specifies what to be done when the laptop lid is closed.
      '';
    };

    services.logind.lidSwitchDocked = mkOption {
      default = "ignore";
      example = "suspend";
      type = logindHandlerType;

      description = ''
        Specifies what to be done when the laptop lid is closed
        and another screen is added.
      '';
    };

    services.logind.lidSwitchExternalPower = mkOption {
      default = config.services.logind.lidSwitch;
      defaultText = literalExpression "services.logind.lidSwitch";
      example = "ignore";
      type = logindHandlerType;

      description = ''
        Specifies what to do when the laptop lid is closed and the system is
        on external power. By default use the same action as specified in
        services.logind.lidSwitch.
      '';
    };

    systemd.sleep.extraConfig = mkOption {
      default = "";
      type = types.lines;
      example = "HibernateDelaySec=1h";
      description = ''
        Extra config options for systemd sleep state logic.
        See sleep.conf.d(5) man page for available options.
      '';
    };

    systemd.user.extraConfig = mkOption {
      default = "";
      type = types.lines;
      example = "DefaultCPUAccounting=yes";
      description = ''
        Extra config options for systemd user instances. See man systemd-user.conf for
        available options.
      '';
    };

    systemd.tmpfiles.rules = mkOption {
      type = types.listOf types.str;
      default = [];
      example = [ "d /tmp 1777 root root 10d" ];
      description = ''
        Rules for creation, deletion and cleaning of volatile and temporary files
        automatically. See
        <citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for the exact format.
      '';
    };

    systemd.tmpfiles.packages = mkOption {
      type = types.listOf types.package;
      default = [];
      example = literalExpression "[ pkgs.lvm2 ]";
      apply = map getLib;
      description = ''
        List of packages containing <command>systemd-tmpfiles</command> rules.

        All files ending in .conf found in
        <filename><replaceable>pkg</replaceable>/lib/tmpfiles.d</filename>
        will be included.
        If this folder does not exist or does not contain any files an error will be returned instead.

        If a <filename>lib</filename> output is available, rules are searched there and only there.
        If there is no <filename>lib</filename> output it will fall back to <filename>out</filename>
        and if that does not exist either, the default output will be used.
      '';
    };

    systemd.user.units = mkOption {
      description = "Definition of systemd per-user units.";
      default = {};
      type = with types; attrsOf (submodule (
        { name, config, ... }:
        { options = concreteUnitOptions;
          config = {
            unit = mkDefault (makeUnit name config);
          };
        }));
    };

    systemd.user.paths = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = pathOptions; } unitConfig ]);
      description = "Definition of systemd per-user path units.";
    };

    systemd.user.services = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = serviceOptions; } unitConfig serviceConfig ] );
      description = "Definition of systemd per-user service units.";
    };

    systemd.user.slices = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = sliceOptions; } unitConfig ] );
      description = "Definition of systemd per-user slice units.";
    };

    systemd.user.sockets = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = socketOptions; } unitConfig ] );
      description = "Definition of systemd per-user socket units.";
    };

    systemd.user.targets = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = targetOptions; } unitConfig] );
      description = "Definition of systemd per-user target units.";
    };

    systemd.user.timers = mkOption {
      default = {};
      type = with types; attrsOf (submodule [ { options = timerOptions; } unitConfig ] );
      description = "Definition of systemd per-user timer units.";
    };

    systemd.additionalUpstreamSystemUnits = mkOption {
      default = [ ];
      type = types.listOf types.str;
      example = [ "debug-shell.service" "systemd-quotacheck.service" ];
      description = ''
        Additional units shipped with systemd that shall be enabled.
      '';
    };

    systemd.suppressedSystemUnits = mkOption {
      default = [ ];
      type = types.listOf types.str;
      example = [ "systemd-backlight@.service" ];
      description = ''
        A list of units to suppress when generating system systemd configuration directory. This has
        priority over upstream units, <option>systemd.units</option>, and
        <option>systemd.additionalUpstreamSystemUnits</option>. The main purpose of this is to
        suppress a upstream systemd unit with any modifications made to it by other NixOS modules.
      '';
    };

    systemd.watchdog.device = mkOption {
      type = types.nullOr types.path;
      default = null;
      example = "/dev/watchdog";
      description = ''
        The path to a hardware watchdog device which will be managed by systemd.
        If not specified, systemd will default to /dev/watchdog.
      '';
    };

    systemd.watchdog.runtimeTime = mkOption {
      type = types.nullOr types.str;
      default = null;
      example = "30s";
      description = ''
        The amount of time which can elapse before a watchdog hardware device
        will automatically reboot the system. Valid time units include "ms",
        "s", "min", "h", "d", and "w".
      '';
    };

    systemd.watchdog.rebootTime = mkOption {
      type = types.nullOr types.str;
      default = null;
      example = "10m";
      description = ''
        The amount of time which can elapse after a reboot has been triggered
        before a watchdog hardware device will automatically reboot the system.
        Valid time units include "ms", "s", "min", "h", "d", and "w".
      '';
    };

    systemd.watchdog.kexecTime = mkOption {
      type = types.nullOr types.str;
      default = null;
      example = "10m";
      description = ''
        The amount of time which can elapse when kexec is being executed before
        a watchdog hardware device will automatically reboot the system. This
        option should only be enabled if reloadTime is also enabled. Valid
        time units include "ms", "s", "min", "h", "d", and "w".
      '';
    };

  };


  config = {

  };

}